BANGKOK—Antigovernment protesters in Thailand revived their push to unseat caretaker Prime Minister Yingluck Shinawatra on Thursday, marching through some of Bangkok's busiest streets to keep the protest movement's momentum building ahead of snap elections called for Feb. 2.

Protest leader Suthep Thaugsuban, a former deputy prime minister, led the rally of about 20,000 protesters as a prelude to a larger rally planned for Sunday. Mr. Suthep has repeatedly called for the vote to be delayed after Ms. Yingluck dissolved parliament...